General approach for the description of size effects in ferroelectric nanosystems

Abstract

We propose general analytical approach for the description of size effect influence on polarization and dielectric susceptibility in ferroelectric nanosystems based on the two-parametric direct variational method and Landau-Ginzburg-Devonshire phenomenology. The essence of the approach is to solve Euler-Largange boundary problem for polarization distribution exactly in paraelectric phase without ferroelectric nonlinearity and then to use the linearized solution for derivation of the approximate analytical expression for spontaneous polarization distribution in ferroelectric phase with the average polarization and characteristic spatial scale as variational parameters. Corresponding polarization distributions calculated within the approach in thin ferroelectric films, nanowires and nanotubes were compared with the available exact solution of Landau-Ginzburg-Devonshire equation or approximate results obtained earlier from the one parametric solution. Perfect agreement between the exact solution and obtained approximate ones is demonstrated. The realization of the proposed scheme of the two-parametric direct variational method seems even simpler than the one-parametric scheme based on the Landau-Ginzburg-Devonshire free energy expansion with renormalized coefficients, while the validity range of two-parametric solution is much wider and the accuracy is higher. So, obtained analytical results have methodological importance for calculation of the phase diagram size effects, polarization distribution, all related polar, dielectric, piezoelectric and pyroelectric properties of single-domain ferroelectric nanoparticles and thin films. The proposed method is applicable to different ferroic nanosystems.

Piezoresponse of ferroelectric films in ferroionic states: Time and voltage dynamics

“…These states are exquisitely sensitive to chemical and electric conditions at the film surfaces [14][15][16][17][18]. The analytical description of coupled ferro-ionic states was developed via the combination of Ginzburg-LandauDevonshire description of the film ferroelectric properties [19,20,21] Here, we explore the dynamic behavior of the ferro-ionic states in thin films, representing the polarization and electromechanical response as measured by the piezoresponse force microscopy (PFM) [23,24]. We demonstrate that the piezoelectric responses in ferroelectric, ferro-ionic and nonferroelectric electret-like ionic states are inseparable at low frequencies of applied voltage.…”

Flexible Ferroelectric BaTiO3 – PVDF Nanocomposites

“…From matrix-loaded composites to highly sophisticated arrangements, composites can be designed to tailor the acoustic impedance, coupling constant and mechanical quality factor, as compared to bulk ceramics. In nanotechnology applications, ferroelectric ceramics have to overcome some size scaling challenges, since their main properties can be dramatically affected when the grain size decreases to a certain limit, where the material suffers either changes in Tc, phase transition or variations in its polarization state (Eliseev & Morozovska, 2009). In a similar manner, ferroelectric polymers have to be processed in a way that enhances its crystalinity and favours the growing of the polar phase.…”

Piezoelectricity above the Curie temperature? Combining flexoelectricity and functional grading to enable high-temperature electromechanical coupling

“…Flexoelectricity has recently received much attention, e.g., it suggests tantalizing possibilities such as creating effectively piezoelectric materials without using piezoelectrics. [5][6][7][8][9][10] In a recent work, Chandratre and Sharma showed, using quantum calculations, that merely by creating triangular holes in graphene nano ribbons, flexoelectricity enabled the ensuing structure to behave like a piezoelectric. 11 Their central idea is simple and the present work takes advantage of the following observation.…”